A fuel injection valve of this kind generally has such a structure, according to which fuel pressure in a pressure control chamber (control-chamber pressure) is controlled so as to operate a valve body, which opens or closes an injection port for injecting fuel. Namely, the control-chamber pressure biases the valve body in a valve-body closing direction. The valve body is moved in a valve-body opening direction when the control-chamber pressure is decreased, while the valve body is moved in the valve-body closing direction when the control-chamber pressure is increased.
The fuel injection valve of this kind is known in the art, for example, as disclosed in the following Japanese Patent Publications:    Japanese Patent Publication No. 2011-169241    Japanese Patent Publication No. 2011-169242    Japanese Patent Publication No. 2011-012670
According to the fuel injection valve of the above prior art, a fixed plate and a movable plate are provided in order to rapidly increase the control-chamber pressure and thereby to improve response for a valve-body closing operation (response for terminating fuel injection). A high pressure passage for supplying high pressure fuel to the pressure control chamber and a low pressure passage for discharging the fuel from the pressure control chamber are formed in the fixed plate.
The movable plate is movably accommodated in the pressure control chamber. The movable plate is moved in a direction away from the fixed plate so as to open the high pressure passage, when a plate-separating force becomes larger than a plate-contacting force. The plate-separating force is a force for pushing the movable plate by fuel pressure away from the fixed plate, which acts on an upper end surface of the movable plate on a side to the fixed plate. The plate-contacting force is a force for pushing the movable plate by fuel pressure (or by fuel pressure and a spring force) toward the fixed plate, which acts on a lower end surface of the movable plate on a side opposite to the fixed plate. On the other hand, the movable plate is moved in the direction to the fixed plate so as to be in contact with the fixed plate and to close the high pressure passage, when the plate-contacting force is larger than the plate-separating force.
When starting fuel injection, a control valve provided at an outlet port of the low pressure passage is opened in a condition that the movable plate is in contact with the fixed plate. Then, the fuel is discharged from the pressure control chamber through the low pressure passage in a condition that the fuel supply from the high pressure passage is blocked off. As a result, the fuel pressure in the pressure control chamber is decreased, so that the valve body is moved to a valve-body opening position to start the fuel injection.
When terminating the fuel injection, on the other hand, the control valve is closed in the condition that the movable plate is in contact with the fixed plate. Then, the movable plate is separated from the fixed plate to thereby open the high pressure passage. As a result, the high pressure fuel is supplied to the pressure control chamber to increase the fuel pressure in the pressure control chamber, so that the valve body is moved to a valve-body closing position to terminate the fuel injection.
In case of a fuel injection valve, in which the movable plate is not provided, the fuel is constantly supplied from the high pressure passage to the pressure control chamber. Therefore, when a diameter of an orifice provided in the high pressure passage is made larger, the fuel pressure in the pressure control chamber is not rapidly decreased when the control valve is opened. As a result, response for starting the fuel injection is getting worse. On the other hand, when the diameter of the orifice is made smaller, the fuel pressure in the pressure control chamber is not rapidly increased when the control valve is closed. Then, response for terminating the fuel injection is getting worse.
Contrary to that, in case of the fuel injection valve of the above prior arts, in which the movable plate is provided, the high pressure passage is closed by the movable plate when the control valve is opened. As a result, when the diameter of the orifice provided in the high pressure passage is made larger, the response for starting the fuel injection is not adversely affected, while the response for terminating the fuel injection can be improved.
In a case that fuel is injected at multiple timings in one combustion cycle, a demand for reducing an interval between fuel injections (hereinafter, the injection interval) is increased. In order to meet the above demand, it is necessary to decrease the control-chamber pressure for carrying out a next fuel injection immediately after having terminated the previous fuel injection. The termination of the fuel injection is carried out by closing the control valve to thereby increase the control-chamber pressure. In other words, it is required that the control-chamber pressure, which has been increased for the purpose of terminating the fuel injection, is rapidly decreased to a valve-body opening pressure (that is, a control-chamber pressure at which the valve body starts its valve-body opening movement).
However, there exists a response delay between change of the control-chamber pressure and an actual opening or closing operation of the valve body. Therefore, due to the response delay, there exists a limit for shortening the injection interval from a timing of the termination of the fuel injection to a timing at which the control-chamber pressure is decreased to the valve-body opening pressure by opening the control valve.
According to the structure of the fuel injection valve disclosed in any one of the above prior arts, the movable plate is in a condition separated from the fixed plate at a time point at which the control valve is closed for the purpose of terminating the fuel injection. It is, therefore, necessary to wait until the movable plate is brought into contact with the fixed plate, in order to open the control valve for the purpose of starting the next fuel injection. The above waiting time for the movement of the movable plate to a plate-contacted condition acts as a drag for shortening the injection interval.